This invention relates generally to manned spacecraft and, more particularly, to emergency descent vehicles for crews of orbiting space stations.
The U.S.-built space station Freedom will require one or more emergency descent vehicles to bring some or all of the crew members safely back to earth in the event of an emergency, such as a medical problem with a crew member or a major malfunction of the station. Several types of emergency descent vehicles are presently being considered. One type is a variant of the U.S.-built Apollo spacecraft. The Apollo spacecraft variant includes an Apollo-type pressurized command module which is attached to an unpressurized service module through the aft heat shield of the command module. The command module provides life support during orbit prior to reentry and is used for reentry and landing on the earth's surface. The service module provides propulsion and electrical power during orbit, and is separated from the command module prior to reentry and allowed to burn up in the atmosphere.
Another type of emergency descent module being considered is a variant of the Russian-built Soyuz spacecraft, which is used to ferry crews back and forth to the Russian space station MIR. The Soyuz spacecraft variant includes a pressurized orbital module, a pressurized descent module, and an unpressurized service module. The orbital module provides life support during orbit prior to reentry, the descent module is used for reentry and landing on the earth's surface, and the service module provides propulsion and electrical power during orbit. The orbital and service modules are separated from the descent module prior to reentry and allowed to burn up in the atmosphere.
One or more of these emergency descent vehicles will be delivered to the space station by the U.S.-built space shuttle and docked at the space station for emergency use. However, previous Apollo and Soyuz spacecraft have been launched on expendable launch vehicles, which induce large axial loads and small lateral loads. The spacecraft were designed to withstand the large axial loads, but the small lateral loads allowed the spacecraft to be relatively long. Unfortunately, the space shuttle can induce large lateral loads, especially during a landing after an aborted mission, thus potentially inducing large bending loads at the module interfaces. Furthermore, the space shuttle cargo bay has a limited length and these relatively long spacecraft do not fit easily in the cargo bay, thus limiting flexibility in loading. In addition, launch costs are based on the length of the cargo, as well as its weight, resulting in much higher launch costs. Finally, the relatively small diameter of the Soyuz spacecraft compared to the shuttle cargo bay requires that a special launch cradle be used, which increases system costs, as well as launch costs because of the additional weight. Accordingly, there has been a need for a shorter, more compact emergency descent vehicle for launch by the space shuttle. The present invention clearly fulfills this need.